4mm aluminum wire is commonly used for bending thicker branches on younger trees. Training wire can make it easy for those looking to create a custom shape with their bonsai. Simply wrap the branches with the wire and bend into a desired shape.

Benefits of Copper Bonsai Wire vs. Aluminum Bonsai Wire: Due to the strength of copper wire, you do not need to use as thick a diameter of wire to bend a branch as you would with aluminum wire. This helps in the aesthetics of the tree so as not to cover the tree with wire. Copper wire will also fade to a more natural color over time.